Current technology utilizes removably connected printed circuit boards. A daughter board is removably connected to a mother board allowing the daughter board to be replaced as needed. Terminals of the connector electrically connect contact areas of the daughter board to contact areas of the mother board. This requires connectors with multiple rows of closely spaced terminals (0.100 inch centerlines or less) therein. The connectors employ stamped and formed terminals which are inserted into plastic, metal or metallized housings using dielectric sleeves which are molded onto the terminals.
In current electronic circuits, the use of increasingly higher speed switching signals has necessitated control of impedance for signal transmission. At the connector interfaces between mother boards and daughter boards this has been accomplished primarily by alternating ground terminals with signal terminals in the connectors in order to provide a signal reference path and shielding for the signal path. Traditionally, large numbers of terminals are used for ground, with as many as eight terminals being used as ground for every one that is used for signal Thus in the prior art, the number of terminals used for signal transmission is drastically limited, which in turn limits the amount of contact areas which can be beneficially connected between the mother board and the daughter board for signal connection purposes.
In an attempt to provide a connector which allows all terminals to be used for signal transmission, a coaxial type connector described in U.S. Pat. No. 4,451,107 was devised. Although some of the above mentioned problems where solved, other serious problems arose. At high speed transmission the right angle of the terminals caused reflection of the signals, limiting the effectiveness of the connector at high speed transmission. Also limiting the effectiveness of the connector is the fact that the molded dielectric constant of the material of the housing cannot by itself be low enough for high speed transmission in the high gigahertz range.
Other problems include insertion and manufacturing difficulties. As the number of terminals required increases, the insertion force of the male connector into the female connector becomes impractical. In other words, the insertion force becomes so great that the mating halves of the connector cannot be mated together, or the housing and contacts are damages as insertion occurs. The manufacturing of the connector described in U.S. Pat. No. 4,451,107 is also made impractical by the manufacturing process of die casting the metal housing, injection molding a nylon sleeve, and casting the terminals through the nylon sleeves in the housing. This process of manufacturing is very difficult to control and can lead to faulty connections. Therefore, the configuration of the invention of the above cited reference is impractical for many reasons.